Maybe precisely because it's not so refined and therefore cheaper to produce? I only buy caster sugar if I'm making a cake. The rest of the time a bog-standard pack of Tate and Lyle seems to keep us going for quite a long time.
They do have a nutritional benefit i.e. 'energy' calories. There isn't much going on in the vitamin and mineral department, admittedly, but it would be incorrect to say they offer zero nutritional value
In the US, caster sugar is called "superfine" or "baker's sugar" and it's a lot more expensive than granulated. I've only ever bought it once and I really couldn't tell the difference. My cakes and pastries have never been crunchy.
So perhaps it's the caster sugar that should be done away with, especially considering it's more processed? I bet your cost would go down
No - there is no nutritional benefit. You can get all the energy you need from things that are far better for you. And it is the excess 'energy' that people eat that is converted to fat. Have sugar by all means, it tastes nice - but don't be under any illusions as to the nutritional value, or the damage it can do.
The problem with the 'sugar gives you energy' argument is that people think it gives you energy. It doesn't. All it does is provide you with fuel if you are being energetic. It won't make you feel like being energetic. If you eat the sugar and then do bugger all, it'll simply be converted into fat.